Project Summary Three sets of experiments are proposed that address clinically relevant questions for hearing-impaired (HI) listeners, especially those who have hearing aids and/or cochlear implants. In HI individuals, spectral information is not necessarily matched between ears due to asymmetries introduced by hearing loss and hearing device programming. Thus, HI listeners integrate mismatched spectral information between ears, in a process that we call binaural spectral integration. Recent studies suggest that binaural spectral integration adapts to reduce perception of interaural spectral mismatch in HI individuals. Specifically, binaural pitch fusion is increased so that pitches that differ greatly in frequency between the two ears are still heard as a single percept. Furthermore, this broadened binaural fusion may reduce binaural benefits in HI listeners for sound localization and speech perception in noise. The general goal of the proposed experiments is to further investigate how binaural pitch fusion can be influenced by temporal properties of the stimuli. Since speech sounds vary in both spectral and temporal domains, measurements of binaural pitch fusion with stimuli having both spectral and temporal characteristics may yield more realistic estimates of binaural fusion, and provide a better understanding of how fusion affects binaural benefits in speech perception for HI listeners. The overall hypothesis suggested by preliminary data is that manipulation of the temporal cues in the stimuli either promotes (Aim 1) or suppresses (Aim 2) binaural fusion in HI listeners. Further, the degree of binaural fusion is hypothesized to correlate with and predict speech perception abilities with spatially-separated sound sources in HI individuals (Aim 3). The specific aims of this proposal are as follows: (1) to determine how amplitude modulation affects binaural pitch fusion, and how the effects differ between hearing impaired and normal hearing listeners, (2) to determine how auditory stream segregation cues affect binaural pitch fusion, and (3) to determine whether there is a relationship between binaural pitch fusion and speech perception abilities in spatially separated noise. This proposal will provide new information about how temporal cues impact binaural spectral integration in HI listeners who use hearing aids and/or cochlear implants.